In view of increasing concerns over the environmental impact of motor vehicles powered by internal combustion engines, there is now increased interest and importance in providing so called “cleaner” motor vehicles which produce less pollution in the form of gases which are deemed harmful to the environment. Accordingly, it is now becoming more and more common to provide motor vehicles which are powered electrically, at least during periods of their operation. For example, it has been proposed to provide electric vehicles which are driven by a large electrical motor drawing its power from a rechargeable battery.
It has also been proposed to provide so-called “hybrid” motor vehicles which typically combine an efficient internal combustion engine with an electric motor. Hybrid vehicles of this type are configured to be driven by the electric motor whenever possible or convenient, but are driven by the internal combustion engine when the propulsive power offered by the motor is insufficient to meet the instant performance demand, for example because the demand simply exceeds the performance limits of the motor, or because the source of electrical energy from which the motor draws its power contains insufficient charge. In such an arrangement, the motor typically draws its electric power from either a rechargeable battery or a series of capacitors, with the battery or capacitors being arranged to charge from an alternator connected to the engine when the combustion engine is running.
As will be appreciated, electrically powered vehicles, and so-called hybrid vehicles of the general type described above therefore require relatively large electrical energy storage units, such as batteries or capacitors, in order to provide sufficient electrical power for the propulsive motor. Accordingly, such storage units are typically configured to be very high voltage (typically approximately 300V) and to store a very significant amount of electrical energy (typically between 2-10 kWh), and as such represent a significant electrical hazard, particularly in the event of the vehicle being involved in a crash, or an internal short-circuit occurring within the battery.
As will be appreciated, electrical storage devices such as capacitors or batteries of the type described above can become extremely hot in the event of a short-circuit occurring either internally, or externally as a result of a crash, and hence represent a risk of fire or explosion in such circumstances.
Another concern with high-energy electrical arrangements of this type is that damage caused to a motor vehicle in the event of an accident can cause parts of the internal circuitry of the vehicle to become damaged and expose live wiring which presents a shock hazard for the driver and passengers of the vehicle, and also to any rescue personnel in attendance.
There is therefore a need for a safety arrangement which addresses these risks.
United States patent application 2001/0055712 discloses a storage cell battery incorporating a safety device.
In United States patent application 2003/0230177, there is disclosed apparatus incorporating an ignitable initiator which acts upon a severing element so as to sever a vehicle battery cable.
United States patent application 2008/0241667 discloses a tunable frangible battery pack system.